Investigation of Background Influence on Flame Measurement

2.4.2 Chemicals

Due to the strict requirements of the measurement, distilled water and chemicals must be of high purity. During the research process, we used the following chemicals:

1. Merck HNO3 Acid 65 %

2. Merck 37% HCl Acid

3. CH 3 COONH 4 solid Merck

4. NH 2 OH.HCl solid Merck

5. CH 3 COOH 100% Merck

6. Merck 1000ppm Pb standard solution

7. Merck Cd 1000ppm standard solution

8. MESS-3 Canadian Standard Sediment Sample

To minimize contamination, all instruments are soaked in 10% HNO 3 for 24 hours before use, then washed with distilled water.

2.4.3 Preparation of chemicals and standard solutions

1. CH 3 COONH 4 1M solution : Dissolve 77g CH 3 COONH 4 in 1 liter of water

keep

2. Acidify 1M CH 3 COONH 4 solution to pH = 5 with HOAc: Use a machine

Measure pH and adjust to pH=5 with HOAc.

3. 25% CH 3 COOH solution : Dilute 250ml of pure CH 3 COOH acid with distilled water to 1 liter of solution.

4. 0.04M NH 2 OH.HCl solution in 25% HOc (V/V): Dissolve 2.58g of solid NH 2 OH.HCl in 1 liter of 25% CH 3 COOH.

5. 20% HNO 3 solution : Dilute 30.77ml of 65% HNO 3 with distilled water to 100ml of solution.

6. CH 3 COONH 4 3.2M solution in 20% HNO 3 : Dissolve 24.64 g of solid CH 3 COONH 4 in 100ml of 20 % HNO 3 solution .

7. Working standard solution Pb 100ppm: Dilute 10ml of Pb 1000ppm with distilled water to the 100ml mark.

8. Working standard solution Cd 10ppm: Dilute 1ml Cd 1000ppm with distilled water to the 100ml mark.

2.5 Statistical processing of obtained results

CHAPTER 3: RESULTS AND DISCUSSION

3.1 Investigation of the influence of background on flame measurement

Prepare solutions from working standard solution Pb 100mg/l, Cd 10mg/l and use CH 3 COONH 4 1M, CH 3 COONH 4 1M solutions acidified to pH = 5 with HOAc, NH 2 OH.HCl 0.04M in HOAc 25%, CH 3 COONH 4 3.2M in HNO 3

20% and aqua regia mixture (3:1 HCl : HNO 3 mixture ) as background, measure AAS and record the absorbance value. The results are shown in table 3.1  3.10

Table 3.1 Lead solutions in CH 3 COONH 4 1M base

Order

Pb concentration (mg/l)	Measured absorbance (A)
1	0	0.000
2	2	0.020
3	4	0.040
4	6	0.062
5	8	0.084
6	10	0.108

Maybe you are interested!

Table 3.2 Acidified lead solutions in CH 3 COONH 4 1M base

Order

Pb concentration (mg/l)	Measured absorbance (A)
1	0	0.000
2	2	0.021
3	4	0.041
4	6	0.063
5	8	0.084
6	10	0.109

Table 3.3 Lead solutions in NH 2 OH.HCl 0.04M base in 25% HOAc

Order

Pb concentration (mg/l)	Measured absorbance (A)
1	0	0.000
2	2	0.021
3	4	0.042
4	6	0.064
5	8	0.087
6	10	0.109

Table 3.4 Lead solutions in the base CH 3 COONH 4 3.2M in HNO 3 20%

Order

Pb concentration (mg/l)	Measured absorbance (A)
1	0	0.000
2	2	0.022
3	4	0.044
4	6	0.066
5	8	0.088
6	10	0.110

Table 3.5 Acidic lead solutions

Order

Pb concentration (mg/l)	Volume of aqua regia (ml)	Absorbance (A) measurable
1	0	1	0.000
2	2	1	0.020
3	4	1	0.043
4	6	1	0.065
5	8	1	0.087

0.109

Table 3.6 Cadmium solutions in CH 3 COONH 4 1M base

Order

Cd concentration (mg/l)	Measured absorbance (A)
1	0	0.000
2	0.2	0.037
3	0.4	0.073
4	0.6	0.111
5	0.8	0.138
6	1	0.183

Table 3.7 Acidified cadmium solutions in CH 3 COONH 4 1M base

Order

Cd concentration (mg/l)	Measured absorbance (A)
1	0	0.000
2	0.2	0.037
3	0.4	0.074
4	0.6	0.114
5	0.8	0.150
6	1	0.184

Table 3.8 Cadmium solutions in NH 2 OH.HCl 0.04M base in 25% HOAc

Order

Cd concentration (mg/l)	Measured absorbance (A)
1	0	0.000
2	0.2	0.038
3	0.4	0.075

0.039

0.038

0.037

0.036

Effect of background on A of Cd at 0.2 mg/l concentration

CH3COONH4 CH3COONH4 NH2OH.HCl

CH3COONH4

3.2M In HNO3 20%

Hydropower

1M acidified 0.04M in

25%

Background

0.079

0.078

0.077

0.076

0.075

0.074

0.073

0.072

0.071

0.070

Effect of background on A of Cd at 0.4 mg/l concentration

CH3COONH4 CH3COONH4 NH2OH.HCl

CH3COONH4

3.2M In HNO3 20%

Hydropower

1M acidified 0.04M in

25%

Background

0.116

0.115

0.114

0.113

0.112

0.111

0.110

0.109

0.108

Effect of background on A of Cd at 0.6 mg/l concentration

CH3COONH4 CH3COONH4 NH2OH.HCl

1M acidified 0.04M in

25%

Background

CH3COONH4 Mixture 3.2M In aqua regia

HNO3 20%

0.160

0.155

0.150

0.145

0.140

0.135

0.130

0.125

Effect of background on A of Cd at 0.8 mg/l concentration

CH3COONH4 CH3COONH4 NH2OH.HCl

CH3COONH4

3.2M In HNO3 20%

Hydropower

1M acidified 0.04M in

25%

Background

0.192

0.190

0.188

0.186

0.184

0.182

0.180

0.178

Effect of background on A of Cd at 1 mg/l concentration

CH3COONH4 CH3COONH4 NH2OH.HCl

CH3COONH4

3.2M In HNO3 20%

Hydropower

1M acidified 0.04M in

25%

Background

0.022

0.021

0.020

0.019

Effect of background on A of Pb at 2 mg/l concentration

CH3COONH4 CH3COONH4 NH2OH.HCl

CH3COONH4

3.2M In HNO3 20%

Hydropower

1M acidified 0.04M in

25%

Background

0.044

0.043

0.042

0.041

0.040

0.039

0.038

Effect of background on A of Pb at 4 mg/l concentration

CH3COONH4 CH3COONH4 NH2OH.HCl

CH3COONH4

3.2M In HNO3 20%

Hydropower

1M acidified 0.04M in

25%

Background

Effect of background on A of Pb at 6 mg/l concentration

0.067

0.066

0.065

0.064

0.063

0.062

0.061

0.060

CH3COONH4 CH3COONH4 NH2OH.HCl

1M acidified 0.04M in

25%

Background

CH3COONH4 Mixture 3.2M In aqua regia HNO3 20%

0.089

0.088

0.087

0.086

0.085

0.084

0.083

0.082

Effect of background on A of Pb at 8 mg/l concentration

CH3COONH4 CH3COONH4 NH2OH.HCl

CH3COONH4

3.2M In HNO3 20%

Hydropower

1M acidified 0.04M in

25%

Background

Absorbance A

0.6	0.115
5	0.8	0.153
6	1	0.186

Table 3.9 Cadmium solutions in CH 3 COONH 4 3.2M base in HNO 3 20%

Order

Cd concentration (mg/l)	Measured absorbance (A)
1	0	0.000
2	0.2	0.038
3	0.4	0.078
4	0.6	0.116
5	0.8	0.156
6	1	0.190

Table 3.10 Acidic cadmium solutions

Order

Cd concentration (mg/l)	Volume of aqua regia (ml)	Absorbance (A) measurable
1	0	1	0.000
2	0.2	1	0.037
3	0.4	1	0.076
4	0.6	1	0.114
5	0.8	1	0.153
6	1	1	0.189

The results are shown in Figure 3.1:

Absorbance A

0.111 Effect of background on A of Pb at concentration of 10 mg/l
0.110

0.109

0.108

0.107

0.106

	CH3COONH4 CH3COONH4 1M 1M acidified	NH2OH.HCl 0.04M in 25% HOc Background	CH3COONH4 3.2M In HNO3 20%	Hydropower

0.105

Figure 3.1 Effect of substrates at each concentration

The obtained A absorbance values show that in general, for the elements at different concentrations, the obtained A values do not change much, they tend to increase gradually from the background CH 3 COONH 4 1M  CH 3 COONH 4 1M acidified  NH 2 OH.HCl 0.04M in 25% HOAc  CH 3 COONH 4 3.2M in 20% HNO 3 and slightly decrease in the background of aqua regia. The A absorbance obtained in the background CH 3 COONH 4 is the lowest, with the background CH 3 COONH 4 3.2M in 20% HNO 3 giving the highest A absorbance.

3.2 Investigation of the combustion gas ratio in flame measurement

3.2.1 Measurement of lead element

Take 5 mg /l Pb solution, adjust the amount of C2H2 gas , keep the amount of compressed air supplied according to the ratios (table 3.11), then measure the absorption A.

Table 3.11 Absorption A of lead varies with the proportion of combustible gas

Gas ratio (C 2 H 2 : air)

Absorbance A
2:10	0.047
1.5:10	0.045
1:10	0.045
0.5:10	0.043

The results showed that the gas ratio C 2 H 2 : air was 2:10 for the largest absorption A.

3.2.2 Measurement of cadmium element

Proceed similarly to the lead element, using 0.5 mg/l cadmium solution, keeping the amount of compressed air supplied in the same proportions, the results are as in table 3.12:

Table 3.12 Absorption A of cadmium varies with the combustion gas ratio

Gas ratio (C 2 H 2 : air)